Questions tagged [rf]

Short for Radio-Frequency. Frequencies at which radiation (intentional or not) plays a role. Typically associated with wireless communications, but also relevant for high-speed PCB design.

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56 views

How does the LM386 work?

I am not an electrical engineer, but I am curious enough and my mind tells me to make a radio circuit. Now I am into it, so to make one, I need some components, but before that so that I can be a ...
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RF Matching Net

I am projecting a system that contains two RF chips, a LoRa SX1276 (915MHz) chip and a ESP32-D0WDQ6 (2.5GHz). In the schematic bellow, the ESP32 (2.4GHz) design has a matching net between the chip ...
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How to calculate Pi filter for RF with PCB antenna - Nordic nRF52832

I have finished the layout of a bluetooth beacon based on SoC nRF52832 of Nordic, there is a Pi filter between the IC pin and the antenna that use the AN043 drawing of Texas. AN043: https://www.ti.com/...
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Power tree understanding

I am projecting a brushless motor driver that contains a LoRa SX1276 radio and a ESP32-D0WDQ6 chip. The power line then gets really noisy when everything is working. For the RF blocks (SX1276 and ...
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Limits on frequency generation using nonlinear device + resonator cavity

I recently saw a schematic of an RF device which supposedly could generate a ~1GHz sine waveform via a 50MHz square wave run through a diode and fed into a cavity resonator. What I'm curious about is ...
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How do I switch a PIN diode using a TTL control signal?

I'm designing a transmit/receive switch for an antenna using a PIN diode. The PIN diode I'm using is UM7512 make: Microsemi. I need to switch between -400V (off) to +5V (on). The switching time should ...
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1answer
60 views

Chaining Power Amplifiers

Problem I found an old (but not in use) garage door controller. The receiver is still intact but can't be reached from souterrain. The sender transmits a single tone on 27MHz in the citizen band. The ...
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Why does radio reception consume so much energy?

On low-power radios, the current consumption for reception is similar to the consumption for transmission. For example, the Texas Instruments CC2652 System-on-Chip datasheet claims these values: ...
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Is EMI/EMC still a big concern for a PC case?

I've recently started looking into researching potential concerns when it comes to using a non-metal material for a custom PC case, specifically wood. I've seen people talk about heat, electrical ...
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79 views

RF Matching Problem

I am having some fundamental issues trying to create an impedance matching network for an 868MHz antenna, I have a PI network between the antenna's connector and the antenna feed point I have measured ...
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2.4GHz radio transmitter and receiver circuits [closed]

I have a drone which is controlled with remote using 2.4 GHz radio signals but I don't have the remote so i want to make one on my own but ran into problem with the radio circuits, is there any ...
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How would you combine DC power, bi-directional serial data, and an RF signal on a single 50-Ohm coax feedline?

I would like to power a remote device and communicate with it over some serial protocol on the far-end of a 50-Ohm coax feedline (RS232, i2c, SPI, etc), while at the same time sending/receiving an RF ...
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1answer
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Radio interference during Waterpurifier Refill [closed]

This is really making me go crazy . I don’t have knowledge about this so the problem is : I have a water purifier in dining room And you can see it is mounted on wall and behind the wall is where we ...
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How to choose an appropiate antenna?

I want to increase the Bluetooth Low Energy transmission range of my ESP32 with IPEX connector. How can I select the right antenna? Do I have to take a look only at a 2,4 GHz WiFi antenna, the antenna ...
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33 views

Reducing power consumption of RF433 module

I'm trying to build a remotely-controlled switch using Atmega328p. For radio communication, I've chosen a generic RF433 transmitter/receiver combo, just like in this tutorial: https://...
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If planar coil is used as antenna, then what kind of antenna should it belong to?

The image below shows the example of planar coil I mean. In my search, I found it is similar to NFC antenna, or in the other words, loop wire antenna. However, I don't see there is a hole in the ...
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Common Carrier Sense Algorithm Implementations [closed]

I am currently looking into Cognitive Radio. More specifically into Spectrum Sensing, i.e. the detection of spectrum holes/available channels. After lots of theory, I am now familiar with the some of ...
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How does a multi-meter diode check work and how to test an RF diode with it?

This is a followup question for Can I debug this simple circuit without VNA and proper RF equipment? which I am still fighting. The diode as a nonlinear element could explain all the weird behavior I ...
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Can I debug this simple circuit without VNA and proper RF equipment?

I am debugging a very simple circuit (existing PCB, not designed by me) that downconverts an AM modulated signal at 900 MHz: The problem: What I measure at "Vo" does not match my LTspice ...
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1answer
29 views

BLE beacon 2.4GHz PCB antenna layout for SoC Nordic nRF52832

Schematic, suggested by the datasheet: PCB is round with 33mm, FR4 1.6mm Bottom side Top side Bottom+top 3d view The antenna drawings is based on AN043 of Texas, HERE. How about the question on ...
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1answer
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How to strongly fix N-type connector to thick RG cable?

Can someone tell me what kind of solder or conductive hardening paste is used here to fix the inner conductor of the cable to the pin. I tried soldering of the pin to such cables with tin, but this ...
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1answer
60 views

How to transform a streaming IP video into a CATV signal?

I wanted to create a circuit, where a network cable was connected, and then the eprom, connected to a video stream in IP, after that streaming, it was converted to RF (CATV). What kind of things ...
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102 views

Why do we need array antennas?

If we can increase the directivity of the single element antenna by increasing its electrical size then why do we need array antennas?
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How does a Philips Hue Tap transmit a radio signal without a battery?

The Philips Hue Tap is a remote control for a Philips Hue lighting system. The buttons can be configured to trigger some action on the Hue bridge, such as turning lights on in a particular room. The ...
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2answers
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N-stage rectifier as AM demodulator?

I want to downconvert a simple 100kbit/s NRZ OOK/ASK signal from 900 MHz. In a previous design I found two options: Option 1: simulate this circuit – Schematic created using CircuitLab Option 2:...
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1answer
81 views

How is the antenna return loss measurement impacted by the cable's return loss?

Say you have an antenna (2.4 GHz) for which you want to know the return loss using a VNA. The connection between your VNA port 1 and the antenna is through a coax cable (e.g., Murata). The cable's own ...
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Design of bias-T (L band,10 MHz,DC)

I want to design a bias-T for satellite application where L band RF (950-2150 MHz),10 MHz, and DC will be multiplexed. I need help in finalizing/selecting the inductor(choke) through which DC (13V/18V,...
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How to avoid RF signal loss in a conductive cage acting like a Faraday shield?

I have a standard chip antenna mounted on a large ground PCB plane. The product is unfortunately encapsulated inside a relatively open (carbon-fiber) conductive cage. Unfortunately, I see an obvious ...
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1answer
37 views

WiFi Near Far Interference?

I have several ESPWROOM32 based modules that connect to a far away access point with an RSSI of -70 (it's about 50 feet away through several walls) and a close by access point with an RSSI of -30 (...
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RF amplifier biasing in QUCs

I have selected an infineon BFP840ESD BJT to work with in the design of a low noise RF amplifier. I'm trying to use Qucs Studio to simulate it. From the datasheet I select my bias conditions with as ...
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Ultra-low power energy harvesting wireless sensor network: technology and options

Background & Context I'm developing a project proposal for my honors thesis (officially commences at the end of July, running for one year) with the aim of designing a wireless sensor network with ...
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What is the role of R1/C1, R3 in this slicer circuit?

I found the following data slicer circuit: simulate this circuit – Schematic created using CircuitLab The input is a simple NRZ (PAM-2) signal between "Vhigh" and "Vlow" (=...
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Z parameters in hspice

I want to find Z parameters in hspice. I used following commands. ...
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How to connect a 4:1 balun to a a log periodic antenna?

I'm following a plan for a home made LTE/4G UHF antenna here: https://www.thingiverse.com/thing:3221812 ...because it looks to be of a very similar to design to a very expensive 4G anntenna I know ...
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How to Filter Harmonics in Wideband VCOs

I have a need for a RF signal generator, but I figured it would be a fun project to design a crude one myself. The main technical challenge I'm stuck on is how to filter out the harmonic content ...
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Pinging a dead cellphone

Can a dead phone still be pinged? I was watching a news clip recently of someone lost in the woods with a dead phone that still managed to be pinged. How it this possible? I'd imagine it's some sort ...
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2answers
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Band-pass filter vs. Serial Low-pass+High-pass filter - Is there a difference?

Is there a difference between a band-pass filter (BPF) and tying a low-pass filter's (LPF) output to the input of a high-pass filter (HPF)? It seems to me that they should do the same thing---or ...
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Why DDR4 Specs recommend that Address, Control and Clock buses be referenced to VDD?

Micron's Technical Note TN-40-40: DDR4 Point-to-Point Design Guide, page 19, says (emphasis mine): Timing Budget Suggested practice is to look at the design from a timing budget standpoint to provide ...
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Any modules which can measure the distance between two modules even through obstacles?

This is for a social distance enforcing project for school. I want to know the distance between Module 1 and Module 2, where each module is worn by a person. Usually ultrasound would be used, but I ...
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S-parameters vs device model

Many vendors provide both S-parameters and simulation models for their devices. Having encountered device models that when simulated, don't result in exactly the same S-parameters as the touchstone ...
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85 views

If antennae work best at full, half or quarter wavelengths, why don't received signals at 1, 1/2 and 1/4 wavelengths interfere with each other?

How does a simple radio receiver-antenna differentiate between incoming wavelengths that are the same wavelength as the antenna, one-half and one-quarter? Or would I just hear static unless I have a ...
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Which 433MHz transmitter module can be used for battery operated wireless communication having vey low current consumption (less than 5mA)

Im designing a wireless water level controller. The WLC detects water between overhead and underground tank. The transmitter will be situated at each of the tanks. After water level sensing , the ...
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2answers
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GND plane and reference potential

I have seen that most of RF printed board circuits have a GND plane which is connected to the power supply ground terminal and serves as a return path for current from different components on the ...
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1answer
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Bias T with pulse train

I want to bias my pulser output which is 0 to 30V pulse train. (Which means I want to make 30 to 60V pulses) First, I used a bias T with 30V DC input: I found that it works as a differentiator which ...
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Design guidelines for RF castellated edge connections

I've seen many examples online of castellated vias at board edges used for module connections. However, all of these seem to be for low frequency signals. When using a castellated via to connect an RF ...
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I ran a 3D gain plot for patch antenna but the result looks truncated. Did I mess up the sweep angles? The theta and phi?

I have been stuck on this for long, using HFSS by the way.
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434MHz Small loop printed antenna design

For antenna design, usually it is half wavelength or quarter wavelength antenna. I am trying to understand small loop printed antenna design for 434MHz frequency where even the quarter wavelength is ...
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1answer
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I have been designing a micro strip patch antenna with inset feed and I have a few HFSS simulation questions

Substrate dielectric: 3.5 Substrate height : 1.5mm Frequency: 2.5GHz I followed a particular video on YouTube to guide me, and used an online calculator for the width and length of patch, inset feed ...
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Why don't we use lenses for RF?

Radio waves are a class of electromagnetic waves. Light also is a class of electromagnetic waves. By shaping a material in which the speed of light changes, we can bend the propagation direction of ...
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GND pin of a RF device

I have a doubt about how to connect the following device (a RF power meter, AD8318) to the external circuitry. Let's consider the device: There is the input RF coaxial cable, the power supply ...

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